MIAMI (Reuters) - Tropical Storm Ingrid, the ninth named storm of the 2007 hurricane season, weakened marginally on Friday as it churned far out in the Atlantic and was not expected to become a hurricane, U.S. forecasters said.

By 5 p.m. EDT, Ingrid was around 710 miles(1,145 km) east of the Lesser Antilles islands of the Caribbean and moving toward the northwest at about 8 miles per hour (13 km per hour), the U.S. National Hurricane Center said.

The storm's top sustained winds decreased to 40 mph (64 kph), and the hurricane center said it expected Ingrid to weakened further because of strong wind shear -- the difference in direction and speed of winds at different altitudes.

Ingrid was expected to stay well short of hurricane strength. Tropical storms become hurricanes when their winds reach 74 mph (119 kph).

The 2007 Atlantic hurricane season, however, has already sprung a few surprises.

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On Thursday, Hurricane Humberto slammed into the Texas-Louisiana border area with an unexpectedly powerful punch that killed at least one person, shut down three refineries and cut power to more than 100,000 customers.

It had been forecast to hit land as a tropical storm, but strengthened into an 85 mph (137-kph) hurricane, a pace that forecasters said was the fastest on record for a storm near land.

The season has also witnessed the first time since records began in 1851 that two maximum-strength Category 5 hurricanes made landfall in the same year.

Hurricanes Dean and Felix, which both reached the top rank on the five-step Saffir-Simpson scale at a frighteningly quick rate, hit Mexico's Yucatan Peninsula and Central America in August and September, respectively.